Refraction of light and Snell's Law - Light

Refraction of light and Snell's Law



In this lesson, we will learn:

  • Key terms in refraction
  • Ray diagrams in refraction
  • Solving Snell’s law problems


Refraction of light: Bending of light as it strikes the surface of separation of two media.  

Waves in two dimensions

Key terms

  • Incident ray: The incoming ray of light
  • Refracted ray: The transmitted ray of light into another medium
  • Medium of incidence: The medium in which light travels before it strikes the boundary.
  • Medium of refraction: The medium through which refracted ray travels.
  • Point of incidence: The intersection of the incident ray and the boundary.
  • Normal: An imaginary line is drawn perpendicular to the boundary at the point of incidence.
  • Angle of incidence (< ii ): The angle between the NORMAL and the incident ray.
  • Angle of refraction (< rr): The angle between the NORMAL and the refracted ray.
  • If the incident ray is perpendicular to the boundary the angle of incidence is ZERO, and the angle of refraction will also be ZERO.
  • Snell’s law: The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant, “n”

  • n=sinθisinθr, \large n = \frac{sin \, \theta _{i} }{sin \, \theta _{r}},

    n” is called the index of refraction

    In the more general cases the Snell’s law can be written as :

nisinθi=nrsinθr n _{i} \, sin \, \theta _{i} = n _{r} sin \, \theta _{r}

ni n _{i} = medium of inidence refractive index

nr n _{r} = medium of refraction refractive index

  • Index of refraction: Physical characteristics of matter which determines the extent to which light gets refracted.
  • Optically dense medium: The medium in which the angle between the ray and normal is smaller is called the optically denser medium.
  • The denser the medium the smaller the speed of light in that medium
  • The denser the medium the bigger the value of “nn”.
  • The refracted ray bends TOWARDS the normal in optically denser medium

nn (index of refraction) =C(speedoflightinair)V(speedoflightinmedium) = \frac{C (speed \,of\, light \,in \,air)} {V(speed \, of \, light \, in \, medium)} , n=CV \quad n = \frac{C}{V}
  • Intro Lesson
    Refraction of Light
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Refraction of light and Snell's Law

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